Estimating physicochemical properties and environmental behavior of non-polar organic compounds transported by methane ebullition in an oil sands reclamation site

Syncrude's Base Mine Lake Demonstration (BML) is the first commercial demonstration of water capped tailings technology (WCTT) in the oil sands industry, with the goal of developing into a self-sustaining aquatic ecosystem over time. The partitioning of organic components of residual bitumen and naphtha present in the fluid fine tailing is a critical control on their potential transport and biodegradation. Methanogenesis and associated methane ebullition observed in BML is associated with transport of residual organic compounds to the lake surface, a process controlled by the physiochemical properties of the compounds involved. Though even comprehensive two-dimensional gas chromatography (GC × GC) is unable to resolve and/or identify every single compound from this mixture, we were able to use a GC × GC-based approach to estimate the physiochemical properties of the non-polar fraction of bitumen associated with gas bubbles trapped within ice from BML to assess their environmental behaviours. The modelled results indicated that the non-polar fraction of the transported bitumen generally exhibits low volatility (-5 < log PL <2.5 Pa), low solubility (-12 < log SwL < -1mol·m3), and high octanol-water partitioning coefficients (5 < log Ko-w <13). Furthermore, combining multiple partitioning coefficients allowed a first-order assessment of the aquatic bioaccumulation potential (ABP) and terrestrial biomagnification potential (TBP) of the compounds detected. The results indicated that the non-polar fraction of the transported bitumen is not likely to cause significant aquatic bioaccumulation or terrestrial biomagnification effects, due mainly to their high hydrophobicity. The ability to assess the environmental behaviour of compounds that cannot be individually identified or whose physiochemical properties have yet to be characterized, is an important capability in situations such as oil sands or elsewhere where complex mixtures of organic compounds are present.